1. Field of Invention
The present invention relates to an automatic exposure control device for a camera. More particularly, the invention relates to an automatic exposure control device for a camera provided with an electromagnetic release device for releasing an exposure control mechanism from restraint, the exposure control device being able to prevent deterioration of automatic exposure control performance which is due to decrease in the power source voltage caused by energizing an electromagnet of the electromagnetic release device.
2. Description of the Prior Art
There has so far been known a single lens reflex camera, for example, which has both an electromagnetic release device and an automatic exposure control device, as disclosed in U.S. Pat. No. 3,682,058. In such a camera, a common battery is generally used as a power source for both the devices.
The electromagnetic release device requires substantial power for energizing the electromagnet therein so that it is impossible to obviate a large decrease or drop in source voltage caused by internal resistance of the battery. The automatic exposure control device comprises a photometering circuit for producing a photo-electric output in response to the brightness of an object to be photographed, an analog memory element such as a capacitor which changes the amount of electric storage in response to the photoelectric output from the photometering circuit before energizing the electromagnet to release the exposure control mechanism and which memorizes the photoelectric output from the photometering circuit immediately before raising the mirror upon energization of the electromagnet, and a circuit for automatically controlling exposure in response to the photoelectric output stored in the analog memory element. The sequence of the operation of the aforementioned type of camera, therefore, is electromagnetic release (drop in power source voltage)--analog memory--automatic exposure control. It is noted here that the photoelectric output is memorized after the electromagnetic release. Therefore, the amount of storage in the analog memory element is varied depending on the drop in power source voltage caused by the energization of the electromagnet, and does not correspond to the photoelectric output. Before the storage amount of the analog memory element becomes correspondent to the photoelectric output, the mirror is raised so that exposure which is controlled based on the storage amount of the analog memory element, is not proper.